Web rotary die cutting and perforating modules are in common use in commercial web printing operations. The usual module supports the anvil cylinder below the plane of a web feed line and the die cylinder above. If embossing or scoring effects are desired, there is no obvious proven method for performing these operations on such an apparatus.
In rotary die cutting or perforating, the diameter of the anvil cylinder should be sized so that its surface speed is equal to that of the web material. The use of an anvil or impression cylinder of full pitch height (diameter)--such as is used for die cutting and perforating--is unsatisfactory for operations such as embossing or scoring. For embossing or scoring, the cylinder must be "undercut" or slightly reduced in diameter to allow for the thickness of the counterpart or "makeready" which operates in conjunction with the basic embossing or scoring die affixed to the die cylinder. Conversely, if the counterpart element is affixed to an anvil cylinder of full pitch height, the surface speed of the counterpart exceeds that of the paper web or other material run through the rotary nip. This mismatch of surface rotational speeds may cause tearing of the web and damage to the counterpart. The so-called "counterpart", as contemplated for use in commercial web printing and similar operations may be either a male embossing element or a female scoring element.
In embossing operations, the curved rigid embossing die plate is secured to the die cylinder by die fastening screw clips or similar means. An overall "honeycomb" pattern of tapped holes can be provided on the die cylinder so that the embossing die may be located (by x-y coordinates) and fastened in the desired position to register with the printed web. Normally, the embossing die will be of the female or intaglio type so that the side of the paper web which is, in practice, pushed into the recesses of the curved die, will be raised in relief. The "pushing" or displacement is done by the counterpart or male makeready element which is formed on the anvil cylinder. As one example, the embossing counterpart is initially formed in the makeready steps by applying a paste of semi-liquid epoxy or similar plastic to the anvil cylinder so that it will be "squished" or formed when rolled into contact with the female embossing die(s) fastened to the die cylinder. Prior to this, the face of the female embossing die has been coated with a release agent or oil to prevent the plastic from adhering to its face. After the impression of the female die has been impressed so as to create a mating male counterpart in the plastic makeready, the latter is allowed to harden and then is trimmed away from all non-embossed areas.
The rotary embossing equipment should be of the adjustable centers type, such as that disclosed in U.S. Pat. No. 4,171,655, so that the two cylinders with the respective mating embossing elements can be separated by an amount equal to the thickness of the paper stock. This assures that the embossing will be accomplished by a male/female displacement of the embossed image area(s) but that the paper stock will not be compressed and possibly cracked in these areas.
In the procedure of scoring, male and female co-acting elements are similarly required; the male scoring rule--as part of the curved die plate fastened to the die cylinder--displaces the paper stock into the female grooved material affixed to the anvil or impression cylinder. The female scoring counterpart, sometimes a pre-grooved "matrix" material, with sticky back adhesive, causes the paper stock to be linearly "de-bossed" or pressed down when co-acting with the male scoring cylinder in proper register relationship to the male score. The thickness of the scoring matrix material similarly requires that the anvil cylinder be slightly undercut; i.e., reduced in diameter, so that the surface speed of the "top" outer diameter of the matrix is "correct". Hence, the need to have a separate, full sized diameter anvil or impression cylinder for die cutting/perforating and another anvil cylinder of slightly smaller diameter for embossing/scoring operations.
In conventional rotary modules, for die cutting, it is common to use removable cylinders mounted in movable bearing blocks, which in turn are supported in slotted frames. The die cylinder usually is placed above the anvil cylinder and the die cylinder is equipped with bearer rings which rotate against the smooth body of the anvil cylinder when locked in operating position.
For reasons of greater stability, micro-adjustability of cylinder center distance and improved performance, a different type of module construction is favored. In accordance with the present invention, the upper anvil cylinder, complete with pre-loaded bearings, is mounted in its own end frames. The assembly is cross-braced for rigidity. When the upper cylinder requires changing, the complete box assembly can be easily put in place rather than requiring the services of a skilled machinist.
The lower die cylinder is permanently mounted in the main frames of the module, including a mounting which allows the cylinder to be micro-adjusted toward or away from the anvil cylinder so as to minutely alter, when required, the distance between the cylinders.
The micro adjustment mechanism is described in U.S. Pat. No. 4,171,655, which is incorporated herein by reference.
It is desirable to have one multipurpose module for performing die cutting, perforating, embossing and scoring functions with interchangeable anvil cylinder assemblies.